This invention relates broadly to a mechanism for operating the rotary tool turret of a lathe and, more specifically, to a pneumatically actuated tool turret operating assembly for a lathe.
Broadly speaking, pneumatically actuated rotary tool turret operating systems for lathes have long been known and used in the prior art. See, for example, U.S. Pat. No. 5,187,847 issued to H. Thumm on Feb. 23, 1993. The prior art system disclosed in the patent to Thumm employs a first rim of teeth fixedly attached relative to a tool turret and a second rim of teeth which is immovable relative to a housing. A locking member is employed which also includes teeth and is arranged for slidable movement between a locking position and an unlocking position by means of an air operated piston. The teeth of the locking member engage the teeth of the first and second rims when in the locking position to immobilize the turret to maintain one of the turret tools in an operative position relative to a work piece held in the lathe. The teeth of the locking member disengage the teeth of at least one of the rims when the locking member is disposed in an unlocked position so that the tool turret can be rotated by a motor and gear train to move another tool mounted on the turret into the operating position in place of a tool which previously occupied that position.
One difficulty that can be encountered using the system of Thumm occurs due to the requirement of a relatively high air pressure on a piston in order to maintain the locking member in engagement with the other two rims of teeth so as render the tool turret immobile. A sudden loss or substantial variation in piston air pressure for any reason can cause the locking member to become decoupled from one or both of the other rims and thus render the turret freely rotatable. If a turret tool happens to be in contact with or in close proximity to a rotating work piece during such an air pressure failure or variation, the system can crash resulting in potentially severe damage to the lathe and even injury to operating personnel who may be present in the work area.
Another difficulty with such a prior art system arises from the use of a three piece tooth coupling arrangement for locking the turret in position because a very slight amount of wear in any of these three components will produce play or looseness in their coupling which can produce play in the turret when supposedly locked to the housing. This, in turn, can produce distortions in a work piece being machined in the lathe. Yet another difficulty encountered with such prior art systems is the relative complexity and expense of providing a gear train and motor for rotating the tool turret when unlocked. Still another difficulty encountered using such prior art systems is in the lack of provision for inhibiting contamination of the internal components from the surrounding work place environment.
By means of the present invention, these and other difficulties encountered using such prior art systems are substantially eliminated.